/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/PreviewMesh.h
Calculate tangents for the underlying component. This will calculate and assign tangents for the preview mesh independent of the tangents mode. But if the tangents mode is set to AutoCalculated then it will try to use the auto calculated tangents.
true if tangents were successfully calculated and assigned to the underlying mesh
bool CalculateTangents()